EP0048204B1 - Pyrotechnically activated cartridge with useful load with a safety - Google Patents

Abstract

This invention relates to the safety of ammunitions. The projectile of a cartridge has a base which houses a safety stop consisting of a transversely slidable valve. A device ensures that the valve cannot be released until the projectile has been subjected to a powerful acceleration. Another safety device very advantageously ensures that the pyrotechnical chain inserted in the base functions only when the pressure of the ejection charge has been able to release a sealing-block. In particular, the invention may be applied to infra red window releasing cartridges.

Description

The present invention relates to the security of ammunition.

To launch different payloads, for example illuminating charges, a cartridge is very often used comprising a tube, the socket bottom of which houses a pyrotechnic ejection charge. And the projectile placed in front of the ejection charge is in turn provided with a delay pyrotechnic chain; initiated by the ejection charge, this will finally ignite after leaving the tube the charge for implementing the projectile.

In FR-A-2294420, the applicant has already described the interposition of a transversely sliding drawer, which does not come into the fire transmission position until after the tube has left the projectile. In this way, the implementation of the payload cannot take place before the projectile has left the cartridge tube. This means, which has been widely used, already provides significant security.

US-A-2 118 062 also describes a safety rocket implementing a slide which a stop retains in a position of rupture of the pyrotechnic chain, between a primary detonator and an auxiliary charge; under the effect of the acceleration of the projectile, this stop disappears and the drawer then aligns a detonator with the primary detonator and the auxiliary charge, to establish the continuity of the pyrotechnic chain.

In this known device, nothing prevents the establishment of the continuity of the pyrotechnic chain as soon as the acceleration of the projectile is sufficient, that this acceleration results from the setting in motion of the latter in the weapon barrel or from an impact accidentally suffered by the projectile, in the possible direction of movement of the stop.

FR-A-672 710 describes a rocket safety system using a shutter which closes a fire transmission channel and the pressure of the combustion gases of a charge drives out, if necessary by means of a hammer, to open the channel and thereby allow the fire of a primer to be transmitted to the charge of the projectile.

In this device, nothing prevents the opening of the channel, that is to say the establishment of the continuity of the pyrotechnic chain, as soon as the charge is initiated, even if this initiation is accidental and results for example accidental release of the corresponding striker, especially if the projectile is impacted in the direction of possible movement of the latter.

However, the possible direction of movement of the striker of this device, like that of the movable stop of the device described by US-A-2 118 062, coincides with that of the striker respectively of the initiation of the charge of the projectile or of the primary detonator. , so that the same accidental shock can both initiate this primer or this primary detonator, respectively, and establish the continuity of the pyrotechnic chain, which considerably reduces the reliability of these two known devices.

However, the current trend is to significantly increase safety. Correspondingly, this complicates the devices used.

The present invention, on the contrary, proposes a particularly satisfactory solution, which is based on simple means, and gives complete satisfaction, by envisaging, in addition to the aforementioned chain break drawer, double security produced by entirely separate parts, and operating following radically different principles.

According to the first proposed safety, the aforementioned drawer is immobilized in the chain breaking position by a stop, axially retained until a force of predetermined intensity, and secured to a counterweight, which eclipses it under the effect of the acceleration due to the start of the coup.

To achieve the second safety, which it is very advantageous to use according to the invention, the pyrotechnic chain further comprises another chain break, ensured by the interposition of a shutter block, the latter also being held axially under a predetermined effort, and capable of being driven out by the pressure of the combustion gases. Preferably, this other chain break is placed between the ejection charge and the start of the delay pyrotechnic chain.

In particular, it can be achieved by the fact that the block, which slides in a bore, has a shoulder housing an O-ring larger than the bore, and abutting thereon, in the position where the block ensures the chain breaks, while the gas pressure forces the passage of the block with its seal in the bore.

On its side, also in a particular embodiment, the stop is advantageously maintained in the immobilization position of the drawer by a toothed washer or a veil capable of yielding under a predetermined force.

According to another characteristic of the invention, the pressure of the gases on the shutter block displaces the latter axially, in the opposite direction to the axial movement of the counterweight due to the acceleration at the start of the stroke.

• - la figure 1 est une vue en coupe du mode de réalisation préférentiel des carouches selon la présente invention;
• - la figure 2 est une autre vue en coupe, dans un plan perpendiculaire à celui de la figure 1;
• - la figure 3 est une vue de détail d'une fraction de la figure 1, destinée à illustrer mieux les éléments désignés généralement par 30;
• - la figure 4 est une section - droite formant la coupe B-B de la figure 1;
• - la figure 5 est une vue en coupe d'une autre section de la figure 2, destinée à illustrer les détails désignés globalement par 60; et
• - la figure 5A illustre plus précisément l'élément 62 de la figure 5.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows, given with reference to the appended drawings, given to illustrate by way of nonlimiting example a preferred embodiment of the present invention, and on which ones:

• - Figure 1 is a sectional view of the preferred embodiment of the cartridges according to the present invention;
• - Figure 2 is another sectional view, in a plane perpendicular to that of Figure 1;
• - Figure 3 is a detail view of a fraction of Figure 1, intended to better illustrate the elements generally designated by 30;
• - Figure 4 is a cross-section forming the section BB of Figure 1;
• - Figure 5 is a sectional view of another section of Figure 2, intended to illustrate the details generally designated by 60; and
• FIG. 5A illustrates more precisely the element 62 of FIG. 5.

The cartridge illustrated in FIGS. 1 and 2 comprises a tube 1, integral with a socket bottom 2, which houses a pyrotechnic ejection charge 4, capable of being excited by an electrical primer 3. Passing through the holes d 'a spangle 5, the gases released by the ejection charge 4 will propel a projectile generally designated by the reference 10, this projectile leaving when the cap 6 placed at the other end is released, and retained by crimping formed at the end of the tube 1.

The projectile 10 comprises in the upper part an envelope defined by a disc 12 and a cylinder 11, this envelope being fixed by a screw 14 on the central shaft 13, which in turn comes in the lower part to receive a screw 15 fixing it on the part 16, perforated in particular in 17. Between the end walls 12 and 17 can be formed any charge, for example an illuminating bar, which will be ignited by gases released by an implementation charge 72, and passing through the orifices 17. The plate 16 is in turn fixed to the base of the projectile, which is designated by the general reference 20, and can be made up of one or more integral parts.

As shown in Figures 2 and 4, this base comprises in the middle part a sliding drawer, designated by 50. This drawer is provided with bores in which are pressed outwards pins 53 and 54, coming to bear on the wall external of the part 20. On the other side, the drawer 50 has a rod 56, projecting outwards, until passing through an orifice 57 formed in the part 20, to finally come to bear on the tube 1 It is immediately seen that when the projectile has left the tube, the drawer 50 will move to the left of FIG. 4 to come into abutment on the wall 20. This therefore results in the orifice 52 coming into alignment position , and thus allows a fire transmission between the relay load 51 of FIG. 5 and the implementation load 72 already mentioned, through a thin web 71.

We will now describe the security elements according to the invention.

If we take the pyrotechnic chain in order, the first of these safety elements is constituted by what has previously been called "the other chain break". In Figure 3, we see the upper part of the volume 25 formed for the development, through the orifices of the part 5, of the gases released by the ejection charge 4. Under the effect of the gassing, the pressure rises in this chamber 25, and before it reaches a value sufficient to move the projectile, it will have acted on the assembly 30, consisting of a shutter block 31, provided with a hollow shoulder 32 housing a seal O-ring 33, which comes to bear on the lower edge of a bore 35. When the pressure in the chamber 25 provides sufficient force on the lower face of the shutter 31, the seal 33 will enter the bore. The block 31 is then driven upwards, where it can be received in a cell 36, provided for this purpose. When it has passed the upper edge of the bore 35, the seal 33 will again prevent the lowering of the obturator block 31.

The gases released by the ejection charge will then not only be able to eject the projectile, but also ignite a pyrotechnic charge 40 forming a delay relay. This load 40 is placed in a radial bore, terminating on the side of the bore 35 housing the obturator block 31. And this radial bore comes to an axial orifice, allowing access to another load forming a transmission relay of fire 51.

For technological reasons, the radial bore which houses the part 40 extends to the opposite end of the block 20, by another bore 41. The main purpose of this is to allow the composition to be put in place. delay 41, as well as its settlement. After construction, the bore 41 is closed by a piston 42 secured to a head 43 with the interposition of a seal.

The relay load 51 is located immediately below the sliding drawer 50, and it will therefore be able to ensure the continued transmission of fire, provided that the drawer 50 has meanwhile been able to move, the projectile having come out of the tube, in order to bring the orifice 52 in the axial position. It will be noted that in reality the ignition of the relay composition 51 can be done at the desired time, since it is placed after the delay charge 40.

If we now return to the start of the shot, the gases released by the ejection charge will very quickly communicate a sharp acceleration to the projectile. This acceleration will be exerted on the counterweight 63 of FIG. 5, which is free to slide in an enclosure 64, any piston effect being eliminated by an orifice 65 passing through the counterweight 63. Of course, if on the contrary one wanted to slow down the movement of the counterweight in order to be sensitive to an acceleration for a certain time, the orifice 65 could be given the appropriate calibrated section. This flyweight 63 will therefore be subject to a downward force, which is proportional to the acceleration communicated to the projectile, as well as to its mass. Screwed onto the counterweight 63, a stop 61 is placed projecting into the housing of the drawer 50 in order to immobilize the latter in the broken chain position. The counterweight 61 is retained in position blocking the drawer by a washer 62, which is a toothed washer as can be seen better in FIG. 5A. This toothed washer will open when the force applied to it by the stop 61 reaches a predetermined threshold, and therefore when the acceleration communicated to all the parts 61 and 63 reaches a predetermined value. Once the stop has returned to the housing defined by the enclosure 64, it can no longer come out, and the drawer 50 is therefore free to come into the fire transmission position.

We can now describe the general operation of the cartridge according to the invention. After initiation of the primer 3, the ejection charge 4 begins to burn, and produces a strong gas evolution in the chamber 25. During the pressure increase, the obturator block 31 of FIG. 3 will be moved towards the top, in order to allow the ignition of the delay charge 40, which will burn for a preset time, for example equal to 5/100 seconds. At the same time or shortly thereafter, the projectile 10 begins to move. Its acceleration very quickly reaches a very large value, sufficient to move the stop against the toothed washer 62, and consequently free the drawer. As soon as it leaves the mouth, the slide will therefore be able to move to the axial position, and authorize the communication of fire between the relay load 51 and the processing load 72.

Shortly after the movement of the slide, the pyrotechnic delay 40 will arrive at the end of combustion and ignite the relay load 51, which will now communicate the fire to the implementation load 72. In turn, this will not only ensure the stripping the payload of the cartridge, but also igniting the lighting bread or the similar charge that it can contain.

Those skilled in the art will understand that the load according to the invention has very high security. This security also intervenes at the level of violent shocks undergone by the cartridge, because the displacement of the shutter block 31 occurs axially, but in the opposite direction to the axial movement required for the counterweight 63 in order to ensure the transmission of fire. As a result, a violent vertical shock can at most only move one of the two elements, but not both. On the other hand, these members are placed in the vicinity of axial planes of the cartridge which are perpendicular to each other.

In a particular embodiment, the O-ring 33 of FIG. 3 is a silicone seal for low temperature, which has the advantage of ensuring good blocking of the shutter block when the latter does not move. This results in almost irreversibility of the movement of the shutter block 31, except of course under the effect of strong accelerations which can occur during the start of the stroke.

The cartridge according to the present invention advantageously applies as an infrared decoy for aircraft, because it allows excellent security, even if the delay 40 is very short, so as to ensure deployment of the infrared decoy very soon after the projectile has left the aircraft, condition that the skilled person will recognize as very useful.

Claims (6)

1. A cartridge with a pyrotechnically activated load, of the type comprising a tube (1) solid with the base of a socket (2) which houses a pyrotechnic ejection charge (4), and in front of this, a projectile (10) provided with a delaying pyrotechnic fuze train initiated by the ejection charge (4) in order to light after exit from the tube the charge (72) putting into operation the projectile, and in which the pyrotechnic fuze train is interrupted at the level of a transversely sliding drawer (50), which comes into position for transmitting the fire only after exit of the projectile from the tube, and in which the drawer (50) is immobilized in its position interrupting the fuze trains by an abutment (61), characterized by the fact that this abutment (61) is held axially up to a force of predetermined intensity, and is solid with a mass (63) which overcomes it under the effect of the acceleration due to firing, and by the fact that the pyrotechnic fuze train has another interruption of the fuze train (30) caused by interposition of an obturator block (31), also held axially under a predetermined force, and susceptible of being moved by the pressure of the combustion gases.

2. A cartridge according to claim 1, characterized by the fact that the said other interruption of the fuze train (30) is placed between the ejection charge (4) and the beginning of the delaying pyrotechnic fuze train.

3. A cartridge according to either of claims 1 and 2, characterized by the fact that the block (31), which slides in a bore (35) has a shoulder (32) housing an O-Ring (33) larger than the bore (35) and abutting this, in the position where the block causes interruption of the fuze train, then the gas pressure forces movement of the block (31) with its O-Ring (33) in the bore (35).

4. A cartridge according to any of claims 1 to 3, characterized by the fact that the abutment (61) is maintained in position immobilizing the drawer (50) by a toothed washer (62) susceptible of yielding under a predetermined force.

5. A cartridge according to any of claims 1 to 4, characterized by the fact that the gas pressure on the obturator block (31) displaces it axially in a direction reverse to the axial movement of the mass (63) on account of acceleration on firing.

6. A cartridge according to any of claims 1 to 5, characterized by the fact that the mass (63) and the obturator block (31) are arranged substantially in axial planes which are respectively at right angles to each other.

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